how to resolve the async await issue in javascript?

Question

The following is my code

let icsFileData = [];
icsFileData = filterAttachmentArray.map(async(file) => {
  let buff = new Buffer(file.data, 'base64');
  let text = buff.toString('ascii');
  const data = await ical.async.parseICS(text);
  const objectKeys = Object.values(data);
  const filterObj =
    objectKeys.length === 1 || objectKeys[0].type === 'VEVENT' ? objectKeys[0] : objectKeys[1];
  const desiredObj = {
    subject: filterObj.summary.val ? filterObj.summary.val : filterObj.summary,
    description: filterObj.description.val ? filterObj.description.val : filterObj.description,
    dateStart: moment(filterObj.start).format('YYYY-MM-DDTHH:mm:ss\\Z'),
    dateEnd: moment(filterObj.end).format('YYYY-MM-DDTHH:mm:ss\\Z'),
    organizer: filterObj.organizer.params.EMAIL ?
      filterObj.organizer.params.EMAIL :
      filterObj.organizer.val.split('mailto:').join(''),
    invites: filterObj.attendee.length === undefined ?
      filterObj.attendee.params.EMAIL ?
      filterObj.attendee.params.EMAIL :
      filterObj.attendee.val.split('mailto:').join('') :
      filterObj.attendee.map(
        (invite) =>
        invite.params.EMAIL ? invite.params.EMAIL : invite.val.split('mailto:').join('')
      ),
    location: filterObj.location.val ? filterObj.location.val : filterObj.location
  };
  icsFileData.push(desiredObj);
});
//const icsFileDataArray = await Promise.all(icsFileData);
console.log('jhgjhgjhgj: ', await icsFileData);

Please check what is the issue, I tried many times always get the same result.

Here is the result this code always returns me

[ Promise { <pending> } ]

can you add a snippet of your code, that's better than a picture, also would help addressing your issue. — ROOT
– ROOT, Commented Mar 13, 2020 at 5:13
Promise{} means that you have to use .then() to check the value. Use something like this const returnFromAwait = await icsFileData(); then try returnFromAwait.then(res => console.log(res)); — Not A Robot
– Not A Robot, Commented Mar 13, 2020 at 5:23
Promise {<resolved>: undefined} proto: Promise [[PromiseStatus]]: "resolved" Getting something like this? [[PromiseValue]]: undefined — Not A Robot
– Not A Robot, Commented Mar 13, 2020 at 5:40

ajai Jothi · Accepted Answer · 2020-03-13 05:49:05Z

2

Things to understand,

async/await are just a syntactical sugar to write async code in synchronous fashion
the callback inside your .map(async() => { ...}) gonna return a Promise.
so in your code, icsFileData is a collection of Promise, so you have to use Promise.all to resolve all the promises to get the desired result

let icsFileData = [];
icsFileData = filterAttachmentArray.map(async(file) => {
  ....
  // you dont need this line, you can simply return the desiredObj
  // icsFileData.push(desiredObj);
  return desiredObj;
});
// this does the magic, since, icsFileData is a array of Promise
const icsFileDataArray = await Promise.all(icsFileData);
console.log('result: ', icsFileDataArray);

answered Mar 13, 2020 at 5:49

ajai Jothi

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